Cold Metal Lock and Pin Repair for Cracked Castings
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Solution Overview
Problem
Existing methods for repairing damaged cast metal components, such as welding or adhesive bonding, are ineffective due to heat-related damage and limited ability to withstand high stress loads.
Innovation Solution
A cold metal repair apparatus and method using elongate metal locks with overlapping circular lobes and stitching pins with a conical shoulder and break-off drive head, which are inserted into lock receiving recesses and threaded bores to provide transverse drawing and strengthening of the casting material portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If welding or brazing is used to repair cracked castings, then the repair can withstand high stress loads, but the heat alters the metal structure and creates discontinuities that weaken the casting strength
Solution Approach 1:
The patent replaces thermal joining processes (welding/brazing) with a mechanical fastening system consisting of metal locks and stitching pins. The metal locks are inserted into drilled holes transverse to the crack, and stitching pins are threaded along the crack, creating a mechanical constraint that holds the casting pieces together without applying heat, thus avoiding thermal damage to the metal structure.
Solution Approach 2:
The patent introduces intermediary components (metal locks and stitching pins) between the cracked casting pieces to transmit and distribute the holding forces. These intermediaries mechanically bridge the crack without requiring direct thermal or chemical bonding, allowing the repair to withstand stress loads while avoiding heat-affected zones.
2Object-affected harmful factors
If adhesive bonding materials such as epoxy are used to repair castings, then the repair process avoids heat damage, but the bonding materials cannot withstand high stress loads
Solution Approach 1:
The patent employs a composite repair system combining metal components (locks and stitching pins) with mechanical fastening methods. This composite approach creates a repair structure that leverages the high strength and rigidity of metal fasteners to withstand stress loads, while avoiding the limitations of adhesive materials, all without requiring heat application.
Solution Approach 2:
The repair system is segmented into multiple discrete mechanical components (metal locks at transverse locations, stitching pins along the crack length) that work together to distribute and bear the stress loads. This segmentation allows the repair to achieve high strength through multiple load-path elements rather than relying on a single adhesive bond.
3Reliability
If castings are replaced instead of repaired in large machines, then the machine can maintain reliability, but the replacement is very time consuming and impractical in operating environments
Solution Approach 1:
The repair system is designed to be installed in-situ within the existing machine structure without requiring disassembly or removal of the casting. The metal locks and stitching pins can be directly installed into the cracked casting at its operational location, allowing the machine to remain in place and maintain operational availability while the repair is performed.
Solution Approach 2:
The repair methodology prepares the cracking area by drilling holes and creating receptacles for the metal locks and stitching pins before final assembly. This preliminary preparation enables the subsequent installation of the mechanical fastening system to proceed efficiently, reducing overall repair time while ensuring proper fit and load distribution.
Data Source
AI summary
A lock and pin for the structural and fluid tight repair of cracks not amenable to high temperature repairs or synthetic material patches. Fluid tight pins and locks seal the crack while one or more locks prevent the crack from growing. These repairs need to endure the remaining life cycle of the machinery part while withstanding all the strain, pressure, heat and expansion and contraction of the part before the crack(s) were formed. Often these cracks evolved due to engineering design flaws that will require even greater strength from these areas than when new.